The present invention relates to a storage system for storing data to be accessed by a computer and more particular, to a diskarray system having a plurality of disk drives or devices.
As one of types of storage systems to be connected to a computer, there is a diskarray system. The diskarray system is also referred to as a RAID (Redundant Arrays of Inexpensive Disks) system, which is a storage system having a plurality of disk devices arranged in an array and a controller (diskarray controller) for controlling the devices. In the diskarray system, a read request (data read request) and a write request (data write request) are processed at high speed through the parallel operation of the disk, and a redundancy is added to the data. Such diskarray systems are classified into 5 levels according to the type of added redundant data and its structure, as disclosed in D. Patterson et al, “A Case for Redundant Arrays of Inexpensive Disks (RAID)”, ACM SIGMOD Conference Proceeding, June 1988, pp. 109–116.
Meanwhile, there is disclosed a technique (refer to JP-A-2002-297320) for reducing a power consumption by shifting a diskarray system to an energy saving mode to suppress power supply to a specific disk.